Up to now, a technique called Structure from Motion (SfM) and its related techniques have been known (see, for example, Patent Literatures 1 to 4 and Non-patent Literatures 1 to 3). According to such techniques, on the basis of a plurality of two-dimensional images obtained by taking images of a subject from different positions and orientations, the positions and the orientations of an image taking apparatus that has taken the two-dimensional images are calculated, and a three-dimensional shape of the subject is reconstructed.